My friend has a Caspar. None of his friends have ever mentioned the friendly ghost. He's 6. And so what if they did? It's no different to any other film or cartoon character. Matilda, Milo, Leo, Ben, Holly, Dorothy, Jamie, Simon. All dc in my dd's school. All well known characters in their own right. That's the thing with names. They name people. Sometimes those people are famous. I perhaps would avoid Adolf or Madonna for example but a benign and well liked ghost? Not a problem.